The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 198 60 099.2, filed on Dec. 23, 1998, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The invention relates to a cylindrical press jacket made of a castable elastomeric material for use on a press device which treats materials in the form of a web. The press device is particularly used for dewatering or smoothing a fibrous material web. The jacket will also have reinforcement threads and/or reinforcement fabric embedded in the elastomeric material and is made with the hardness of the material in the area of the interior side being different from the exterior side of the press jacket. A process for manufacturing the press jacket is also disclosed.
2. Discussion of Background Information
Press jackets are generally known, for example, from DE-OS 196 54 194 and DE-OS 196 54 751; in particular, which use reinforcement threads and cast the press jacket from a homogeneous material. They use relatively large distances between the reinforcement threads to facilitate their manufacture which allows the material to sufficient penetration the spaces formed between these distances.
The manufacturing the jacket in a single casting process also has the advantages of being simpler to manufacturing and producing a jacket with improved strength.
However, depending on the application, it may be necessary to make the jacket with different hardness characteristics between interior and exterior sides. For example, a harder exterior side has advantage with regard to improved abrasion resistance. This characteristic is especially desired when the press jacket is to have grooves or blind holes for receiving the pressed-out water. In contrast, a harder interior side allows for less oil absorption and improves the running properties of hydraulically supported press jackets.
The invention provides for a press jacket and a manufacturing process in which the press jacket has different hardness characteristics between its interior and exterior sides. Moreover, the jacket is made from an elastomeric material which contains at least one component which causes stronger crystallization in the area of the casting mold during casting on a relatively cold casting mold.
The jacket ideally cast against a mold which is colder than the Jacket material being cast. The surface formed against the colder mold generally experiences stronger crystallization, and the result is a generally higher proportion of hard segments being formed on this surface. Thus the surface which is formed against the mold will be harder than the other parts of the jacket.
The elastomer material may be, for example, polyurethane and made include polymers or prepolymers, such as diphenylmethan-diisozyanate (MDI) with polyester, since they are appropriate as components for strengthen crystallization. In addition, the elastomeric material should also contain a cross-linker.
The differences in the hardness between the interior and exterior sides should be in the range of approximately 2 to 7 Shore A. For example, one side may have a hardness in the range of approximately 92 to 96 shore A, while the other side has a hardness of approximately 94 to 98 shore A. However, each surface may also be as low as approximately 85 shore A is desired.
By manipulating the manufacturing process, it is therefore possible to influence which side is to be made harder. Thus in order to manufacture a harder interior side, the elastomeric material is applied to the exterior side of a cylindrical casting mold, since a surface which is formed against a mold surface will be made harder. If it is desired to make the exterior side harder, then the elastomeric material is applied to the interior side of a hollow cylindrical casting mold, again since a surface which is formed against a mold surface will be made harder. Preferably the jacket is cast using conventional centrifugal or hot-casting techniques such as those discussed in U.S. Pat. No. 5,766,421. Moreover, the particulars of such conventional molding are identified in each of U.S. Pat. No. 5,118,391 and 5,134,010, which are fully incorporated by reference. These conventional techniques being modified by the use of a mold which is colder than the casting material as described herein.
In either case the temperature of the casting mold should be controlled between approximately 10 and 100xc2x0 C., and preferably between approximately 20 and 80xc2x0 C., colder than the temperature of the elastomeric material being cast. For it is this cold mold effect which causes a elastomer material formed against it to become harder. Preferably, the mold is preheated to the desired temperature. For this purpose, a heavy steel mold is preferred since it can maintain the desired temperature for a relatively long period of time.
Even more control over the formation of the various degrees of hardness is improved by the use of reinforcement threads or the reinforcement fabric, because this acts as an insulating layer and therefore limits the temperature effect of the cold casting mold to the area between the contact or forming surface and the reinforcement threads or reinforcement fabric. The reinforcing fibers made be those which are conventionally and can include polyester, polyamid, and/or aramid.
According to one aspect of the invention, there is provided a cylindrical press jacket for treating a material web which includes a hollow cylindrical sleeve made of an castable elastomeric material containing at least one crystallization component, wherein the sleeve has an interior cylindrical surface and an exterior cylindrical surface, and one of reinforcement threads and reinforcement fabric embedded in the elastomeric material, such that the hardness of the elastomeric material in an area of the interior surface differs from a hardness of the exterior surface. The jacket may be made using a casting mold which is colder than the elastomeric material being cast. The cold casting mold may be positioned against the interior surface so as to cause a greater crystallization to occur on the interior surface relative to the exterior surface. Alternatively, the cold casting mold may also be positioned against the exterior surface so as to cause a greater crystallization to occur in on the exterior surface relative to the interior surface. Moreover, the jacket may be used for one of dewatering and smoothing a fibrous material web. The greater crystallization may correspond to greater hardness.
The invention also provides that the crystallization component includes a polymer. The polymer may be a prepolymer. The difference between the hardness of the interior surface and the exterior surface may be in a range of approximately 2 to 7 Shore A.
According to another aspect of the invention, there is provided a process for manufacturing a press jacket which includes using a cylindrical casting mold having an exterior surface, setting a temperature of the cylindrical casting mold which is colder than an elastomeric material being cast, casting a hollow cylindrical sleeve from the elastomeric material on the casting mold, such that the elastomeric material contains at least one crystallization component, embedding one of reinforcement threads and reinforcement fabric in the elastomeric material, providing the sleeve with an interior cylindrical surface and an exterior cylindrical surface, such that the internal surface is formed against the external surface of the cylindrical casting mold, wherein the internal surface of the sleeve is harder than the external surface of the jacket.
According to still another aspect of the invention, there is provided a process for manufacturing a press jacket which includes providing a cylindrical casting mold having a hollow internal surface, such that the casting mold has a temperature which is colder than an elastomeric material being cast, casting a hollow cylindrical sleeve from the elastomeric material on the casting mold, such that the elastomeric material contains at least one crystallization component, embedding one of reinforcement threads and reinforcement fabric in the elastomeric material, providing the sleeve with an interior cylindrical surface and an exterior cylindrical surface, such that the external surface is formed against the hollow internal surface of the hollow cylindrical casting mold, wherein the external surface of the sleeve is harder than the external surface of the sleeve. The process may provide that the mold temperature is between approximately 10 and 100xc2x0 C. colder than a temperature of the elastomeric material being cast. Additionally, the mold temperature may be between approximately 20 and 80xc2x0 C. colder than a temperature of the elastomeric material being cast. Alternatively, the mold temperature may be between approximately 10 and 100xc2x0 C. colder than a temperature of the elastomeric material being cast. The mold temperature may also ideally be between approximately 20 and 80xc2x0 C. colder than a temperature of the elastomeric material being cast.
The invention also provides for a roll press jacket which includes a hollow cylindrical sleeve made of an castable elastomeric material containing at least one crystallization component, such that the sleeve has an interior cylindrical surface and an exterior cylindrical surface, wherein the internal surface and the external surface have different hardness characteristics. The jacket may further include one of reinforcement threads and reinforcement fabric embedded in the elastomeric material. The one of reinforcement threads and reinforcement fabric may include one of polyester, polyamid, and aramid. The jacket may be made using a casting mold which is colder than the elastomeric material being cast. Moreover, the interior side may have a hardness in the range of approximately 92 to 96 shore A. Additionally, the interior side may have a hardness in the range of approximately 94 to 98 shore A. The exterior side may have a hardness in the range of approximately 92 to 96 shore A. The exterior side may also have a hardness in the range of approximately 94 to 98 shore A. Furthermore, the cold casting mold may be positioned against the interior surface so as to cause a greater crystallization to occur in on the interior surface relative to the exterior surface. The greater crystallization may correspond to greater hardness. The cold casting mold may be positioned against the exterior surface so as to cause a greater crystallization to occur in on the exterior surface relative to the interior surface. The greater crystallization may further correspond to greater hardness.
The jacket may be used for one of dewatering and smoothing a fibrous material web. The crystallization component may include a polymer. The polymer may be a prepolymer. The prepolymer may include diphenylmethan or diisozyanate (MDI) with polyester. Moreover, the elastomer material may include polyurethane. The jacket may provide for difference between the hardness of the interior surface and the exterior surface to be in a range of approximately 2 to 7 Shore A. The interior side may have a hardness in the range of approximately 92 to 96 shore A. The interior side may also have a hardness in the range of approximately 94 to 98 shore A. Furthermore, the exterior side may have a hardness in the range of approximately 92 to 96 shore A. The exterior side may also have a hardness in the range of approximately 94 to 98 shore A.
The invention also provides for a process for manufacturing a press jacket which includes using a cylindrical casting mold having an exterior surface, setting a temperature of the cylindrical casting mold which is colder than an elastomeric material being cast, casting a hollow cylindrical sleeve from the elastomeric material on the casting mold, such that the elastomeric material containing at least one crystallization component, providing the sleeve with an interior cylindrical surface and an exterior cylindrical surface, such that the internal surface is formed against the external surface of the cylindrical casting mold, wherein the internal surface of the sleeve is harder than the external surface of the sleeve. The method may also provide for embedding one of reinforcement threads and reinforcement fabric in the elastomeric material. Moreover, the mold temperature may be between approximately 10 and 100xc2x0 C. colder than a temperature of the elastomeric material being cast. The mold temperature may also be between approximately 20 and 80xc2x0 C. colder than a temperature of the elastomeric material being cast.
According to another aspect of the invention, there is provided a process for manufacturing a press jacket which includes using a cylindrical casting mold having a hollow internal surface, setting a temperature of the cylindrical casting mold which is colder than an elastomeric material being cast, the temperature being maintained, casting a hollow cylindrical sleeve from the elastomeric material on the casting mold, such that the elastomeric material contains at least one crystallization component, providing the sleeve with an interior cylindrical surface and an exterior cylindrical surface, such that the external surface is formed against the internal surface of the cylindrical casting mold, wherein the external surface of the sleeve is harder than the internal surface of the sleeve. The method may also include embedding one of, reinforcement threads and reinforcement fabric in the elastomeric material.
The process may provide that the mold temperature is between approximately 10 and 100xc2x0 C. colder than a temperature of the elastomeric material being cast. The mold temperature may also be between approximately 20 and 80xc2x0 C. colder than a temperature of the elastomeric material being cast.
The invention also provides for a cylindrical press jacket for treating a material web, which includes a hollow cylindrical sleeve made of an castable elastomeric material containing a prepolymer, the sleeve having an interior cylindrical surface and an exterior cylindrical surface, one of reinforcement threads and reinforcement fabric embedded in the elastomeric material, wherein the jacket is made using a cylindrical casting mold which is maintained at a temperature that is approximately 20 to 80xc2x0 C. colder than the elastomeric material being cast, such that a sleeve surface which is formed against the casting mold has a hardness in the range of approximately 2 to 7 Shore A greater than a sleeve surface which does not contact the casting mold.
Moreover the invention also provides for a process for manufacturing a press jacket which includes using a cylindrical casting mold having a casting surface, setting a temperature of the cylindrical casting mold which is colder than an elastomeric material being cast, wherein the mold has a temperature which is maintained at a temperature approximately 20 to 80xc2x0 C. that is colder than an elastomeric material being cast, casting a hollow cylindrical sleeve from the elastomeric material on the casting mold, wherein the elastomeric material contains a prepolymer, providing the sleeve with an interior cylindrical surface and an exterior cylindrical surface, with either one of the external and internal surfaces being formed against the casting surface of the cylindrical casting mold, creating greater crystallization in the sleeve surface which contacts the cold mold surface, wherein the greater crystallization corresponds to greater hardness in the sleeve surface relative to other portions of the elastomer material, such that the greater hardness is in the range of approximately 2 to 7 Shore A.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.